This invention relates to a combined check valve and siphon preventing valve assembly and more particularly concerns such a valve assembly having a single valve member and improved flow patterns.
Antisiphon check valves are widely used to prevent siphoning of possibly contaminated liquid back into a liquid pressure system. These valves are required by law in many applications, such as, for example, in the connection of recreational vehicle internal water supply systems to a pressurized community water supply system. Valves of this type incorporate a check valve that prevents back flow of water from the using system into the supply system and air ports to prevent siphoning. Undesired siphoning may occur under certain combinations of circumstances unless an antisiphon valve is used. For example, where the check valve malfunctions and the community water supply pressure drops below that of the using system, incipient siphoning may occur, tending to cause water to flow from the using system back into the community system, with a possible contamination of the latter. To eliminate this potential danger, an antisiphoning mechanism is often employed in the connection between a using system and a community system. Such an antisiphon device includes an air or relief port in the valve, this port being normally closed during full flow from the community supply to the using supply, but being open to the atmosphere to avoid potential siphoning conditions.
In a common metallic valve of this type, such as an antisiphon check valve sold by Modern Spec Sales, a flexible diaphragm valve member cooperates with a valve seat to block reverse flow of water through the valve body. The diaphragm valve member is held in place by a retainer plug that screws into the valve body. To provide antisiphon air ports, the retainer plug is provided with ports in communication with the atmosphere and surrounding the valve outlet port, which passes through the relief plug. The valve inlet port is at one end of the valve body and the air ports are at the other end, the outlet end of the valve body. Therefore, in some intermediate flow conditions, water from the inlet port will flow out through both the outlet port and the air port. This flow through the air port, which is toward the using system, and thus toward the user, is highly undesirable even though it only occurs at certain intermediate flow conditions. For this reason, this prior valve of Modern Spec Sales incorporates a separate flow deflector shield mounted at the outlet end of the valve for deflecting water flowing outwardly toward the user from the air ports. This shield adds to the complexity and cost of the valve.
Various valves with dual valve members and of dubious reliability have been suggested. For example, the valve of the patent to Crist U.S. Pat. No. 3,951,164, employs two separate and independently operable air valve and check valve members in a single valve assembly to provide both antisiphon and backflow prevention. The increased number of parts greatly adds to the probability of failure of such a valve and the reliance upon gravity for operation of the valve members further decreases reliability.
Accordingly, it is an object of the present invention to provide an antisiphon check valve that eliminates or minimizes deficiencies of prior valves.